It is helpful to sometimes place a releasable anchor in a well casing pipe at a specified location. Sometimes an anchor will be set in a well and left indefinitely, perhaps for the life of the well. At other times, it will be left only a week or two and thereafter removed. A releasable well anchor of the sort to which the present invention relates which can be set and released with a degree of certainty on the part of the operator at the well head is quite useful. After retrieval, the anchor of the present invention can be subsequently reused time and time again.
Some well anchors function on release without regard to bottom hole pressure differential. This can be hazardous inasmuch as the anchor can be differentially loaded by the bottom hole pressure. The present invention is able to cope with this problem. The well anchor tool incorporates apparatus which responds to bottom hole pressure, locking the tool so that retrieval is not possible so long as pressure differential across the tool exists. This can be overcome by closing off the well at some point thereabove, thereby eliminating the differential. When the differential has been relieved, the tool can be released. With this precaution, the operator avoids the danger of releasing an anchor which would become free and possibly act as a missile in the pipe under the urging of the pressure differential.